Multi-segment turns

ABSTRACT

A method of path planning for a vehicle includes receiving a request for a turn from a current swath to a next swath, receiving information of the current swath and information of the next swath, determining a trajectory of the turn based on the information of the current swath and the information of the next swath, and outputting the trajectory to a control system of the vehicle for executing the turn. The trajectory includes a first segment and a second segment. The first segment starts from a beginning position of the turn at the current swath and ends at an intermediate position; and the second segment starts from the intermediate position and ends at an ending position of the turn at the next swath. The vehicle changes from a forward gear to a reverse gear, or vice versa, as the vehicle transitions from the first segment to the second segment.

CROSS-REFERENCES TO RELATED APPLICATIONS

The following U.S. Patent Application is being filed concurrently, andthe entire disclosure of the other application is incorporated byreference into this application for all purposes:

application Ser. No. 16/863,049, filed Apr. 30, 2020, entitled“HEADLAND-FOLLOWING TURNS”.

BACKGROUND

Engineering vehicles such as tractors are widely used in agriculture andconstruction. For example, a variety of farm implements may be towedbehind or mounted on a tractor to perform various agricultural tasks,such as plowing, irrigation, fertilizer and pesticide spraying, seedspraying, harvesting, and the like. Autonomous or semi-autonomoustractors are used for precision agriculture. As another example,compactors may be used to create a level grade in construction projects.Various path planning algorithms may be used to guide an autonomousvehicle. An end-of-row-turn (EORT) path planner may automaticallycalculate the best possible path to turn the vehicle around from acurrent swath and approach the next swath. The goals of an EORT pathplanner may include producing a trajectory that saves time and fuelcost, and reduces damage to crops or avoids other machines andstructures.

SUMMARY

According to some embodiments, a method of path planning for anautonomous vehicle to make a turn includes receiving a request for atwo-segment turn of a vehicle from a current swath to a next swath in awork area, and in response to receiving the request, receivinginformation of the current swath and information of the next swath, anddetermining a trajectory of the turn based on the information of thecurrent swath and the information of the next swath. The trajectoryincludes a first segment and a second segment. The first segment startsfrom a beginning position of the turn at the current swath and ends atan intermediate position; and the second segment starts from theintermediate position and ends at an ending position of the turn at thenext swath. The vehicle changes from a forward gear to a reverse gear,or vice versa, as the vehicle transitions from the first segment to thesecond segment. The method further includes outputting the trajectory toa control system of the vehicle for executing the turn by following thefirst segment and the second segment of the trajectory successively.

According to some embodiments, a method of path planning for anautonomous vehicle to make a turn includes receiving a request for athree-segment turn of a vehicle from a current swath to a next swath ina work area. The request specifies that the turn is to follow a guidanceline in a headland at a periphery of the work area. The method furtherincludes, in response to receiving the request, receiving information ofthe current swath, information of the next swath, and information of theguidance line, and determining a trajectory of the turn based on theinformation of the current swath, the information of the next swath, andthe information of the guidance line. The trajectory includes a firstsegment, a second segment, and a third segment. The first segment startsfrom a beginning position of the turn at the current swath and ends at afirst intermediate position on the guidance line. The second segmentstarts from the first intermediate position, moving along the guidanceline, and ends at a second intermediate position on the guidance line.The vehicle changes from a forward gear to a reverse gear, or viceversa, as the vehicle transitions from the first segment to the secondsegment. The third segment starts from the second intermediate positionand ends at an ending position of the turn at the next swath. Thevehicle changes from the reverse gear to the forward gear, or viceversa, as the vehicle transitions from the second segment to the thirdsegment. The method further includes outputting the trajectory to acontrol system of the vehicle for executing the turn by following thefirst segment, the second segment, and the third segment of thetrajectory successively.

According to some embodiments, a method of path planning for anautonomous vehicle to make a turn includes receiving a request for aturn of a vehicle from a current swath to a next swath in a work area.The work area has a headland at a periphery thereof, and the headland ischaracterized by a guidance line therethrough. The method furtherincludes, in response to receiving the request, receiving information ofthe current swath, information of the next swath, and information of theguidance line, and determining a trajectory of the turn based on theinformation of the current swath, the information of the next swath, andthe information of the guidance line. The trajectory includes one ormore segments. At least a portion of a first segment of the one or moresegments follows the guidance line in the headland. The method furtherincludes, outputting the trajectory to a control system of the vehiclefor executing the turn.

According to some embodiments, a system for path planning for a vehicleincludes a user interface configured to enable a user to initiate arequest for a turn from a current swath to a next swath in a work area.The work area has a headland at a periphery thereof. The system furtherincludes a memory storing information of a guidance line in theheadland, and a path planning module coupled to the memory and the userinterface. The path planning module is configured to, in response toreceiving the request for the turn, receive information of the currentswath and information of the next swath, and determine a trajectory ofthe turn based on the information of the current swath, the informationof the next swath, and the information of the guidance line. Thetrajectory includes one or more segments. At least a portion of a firstsegment of the one or more segments follows the guidance line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary field.

FIG. 2A illustrates an example of a U-shaped one-segment turn.

FIGS. 2B and 2C illustrate some examples of bulb-shaped one-segmentturns.

FIGS. 3A-3C illustrate some examples of two-segment turns according tosome embodiments.

FIGS. 4A-4C illustrate some additional examples of two-segment turnsaccording to some embodiments.

FIGS. 5A and 5B illustrate some examples of three-segment turnsaccording to some embodiments.

FIGS. 6A and 6B illustrate some examples of one-segmentheadland-following (HF) turns according to some embodiments.

FIGS. 7A and 7B illustrate some examples of two-segment HF turnsaccording to some embodiments.

FIGS. 8A-8C illustrate some examples of three-segment HF turns accordingto some embodiments.

FIG. 9A illustrates an exemplary one-segment HF turn with themove-to-start-of-turn (MST) feature according to some embodiments.

FIG. 9B illustrates an exemplary two-segment HF turn with the MSTfeature according to some embodiments.

FIG. 10 illustrates an exemplary two-segment turn that follows aheadland pattern with the move-to-end-of-swath-before-turn (MESBT)feature according to some embodiments.

FIG. 11 illustrates an exemplary three-segment HF turn with both theMESBT feature and the move-to-beginning-of-next-swath-after-turn (MBSAT)feature according to some embodiments.

FIG. 12 illustrates some exemplary two-segment turns with theturn-within-boundary (TWB) option turned on and off, respectively.

FIGS. 13A and 13B illustrate exemplary one-segment turns for curvedswaths according to some embodiments.

FIGS. 13C and 13D illustrate exemplary one-segment turns fornon-parallel swaths according to some embodiments.

FIG. 14 shows an exemplary user interface (UI) for a user to select adesired type of turn according to some embodiments.

FIGS. 15A and 15B illustrate schematically a vehicle model according tosome embodiments.

FIGS. 16A-16D illustrate four types of trajectory optimization accordingto some embodiments.

FIG. 17 shows a simplified diagram of a system for an autonomous vehicleaccording to some embodiments.

FIG. 18 is a simplified flowchart illustrating a method of path planningfor an autonomous vehicle to make a turn according to some embodiments.

FIG. 19 is a simplified flowchart illustrating a method of path planningfor an autonomous vehicle to make a turn according to some embodiments.

FIG. 20 is a simplified flowchart illustrating a method of path planningfor an autonomous vehicle to make a turn according to some embodiments.

DETAILED DESCRIPTION

Embodiments of the present invention provide path planning to enable anautonomous vehicle to make a turn from one swath to another swath in anoptimal amount of time and minimal travel distance, with minimal cropdamage and/or avoiding obstacles (e.g., avoiding other machines,equipment, and structures on a construction site). In some embodiments,a user may be able to select a multi-segment turn, in which the vehiclemay transition from a forward segment (i.e., the vehicle moving in thedirection it is facing) to a reverse segment (i.e., the vehicle movingin an opposite direction from the direction it is facing), or viceversa. In some embodiments, the user may be able to select aheadland-following (HF) turn, in which at least a portion of thetrajectory of the turn follows a guidance line in the headland (seedefinitions of “headland” and “guidance line” below). The path planningalgorithms are applicable to curved guidance lines, as well as straightguidance lines. They are also applicable to curved swaths as well asstraight swaths, and parallel swaths as well as non-parallel swaths.

The term “geofence” may refer to a geographical boundary of a work area(e.g., an agricultural field, a construction site, and the like) that nopart of the vehicle is permitted to go beyond. The term “boundary” mayrefer to any polygon that is either identical to the geofence or isinwardly offset from the geofence. For example, a farmer may drive thevehicle around the crop rows to record a boundary of the work area. Inconstruction applications, information of the boundary may be availableby construction surveys and the site design. Information of the boundarymay also be obtained by manually walking up the boundary, by using anautonomous ground vehicle (AGV), or the like. The boundary informationmay be input to a path planner for algorithmic computation. The boundarymay be used as the geofence. The term “headland” may refer to the regionbetween the geofence and a second boundary inwardly offset from thegeofence.

FIG. 1 illustrates an exemplary work area 100. The work area 100 has aboundary or geofence 110. A second boundary 120 is inwardly offset fromthe geofence 110. The region inside the second boundary 120 may be thecropped area 130 with many swaths 132. The region between the geofence110 and the second boundary 120 may be referred to herein as theheadland 140. The geofence 110 may be referred to as the outer boundaryof the headland 140. The second boundary 120 may be referred to as theinner boundary of the headland 140 or as the headland boundary. Theoffset distance between the geofence 110 and the second boundary 120 maybe referred to as the width of the headland 140. A headland 140 may havea width that is an integer multiple of the implement width X being used.For instance, in the example illustrated in FIG. 1, the width of theheadland is equal to the implement width X.

The term “headland pattern” may refer to a guidance line 150 inside theheadland 140 that may be used as a route for a vehicle to traverse alongto fill the headland 140. For instance, in the example illustrated inFIG. 1, the guidance line 150 may be offset from the headland boundary120 by a distance that is equal to one half of the implement width X.There may be multiple guidance lines depending on the relationshipbetween the width of the headland 140 and the implement width X.

When an autonomous vehicle needs to make an end-of-row turn to switchfrom a current swath to a next swath, the trajectory of the turn mayfollow a U-shape or a bulb-shape. FIG. 2A illustrates an example of aU-shaped turn. The vehicle 290 is moving in the forward direction (i.e.,in the direction it is facing) on the current swath 202 before the turn.The vehicle 290 continue to move in the forward direction along theU-shaped trajectory 210 of the turn to reach the next swath 204. Inorder to avoid or minimize crop damage, it may be desirable that thetrajectory 210 of the turn is confined to the headland 240 if possible.The U-shaped turn may be possible when the distance D between thecurrent swath 202 and the next swath 204 is wide enough.

When the distance D between the current swath 202 and the next swath 204is not wide enough, the vehicle 290 may need to make a bulb-shaped turn,as illustrated in FIG. 2B. Here, along the trajectory 220 of the turn,the vehicle 290 first turns slightly to the left away from the nextswath 204, then turns around and overshoot to the right slightly, beforereaching the next swath 204. In order for the trajectory 220 to beconfined to the headland 250, the bulb-shaped turn may require a widerwidth W of the headland 250 as compared to the U-shaped turn illustratedin FIG. 2A. As illustrated in FIG. 2C, for a narrower headland 260, someparts of the trajectory 220 may traverse the crop area 270, andtherefore may cause more damage to the crop.

The U-shaped turn illustrated in FIG. 2A and the bulb-shaped turnillustrated in FIGS. 2B and 2C may be referred to as one-segment turntype, since the vehicle 290 stays in the same gear (e.g., the forwardgear) along the trajectory of the turn.

Multi-Segment Turns

According to some embodiments, a path planner may allow multi-segmentturn types. A trajectory of a multi-segment turn may include two or moresegments, in which the vehicle may switch from the forward gear to thereverse gear, or vice versa, as it transitions from one segment to anext segment.

FIG. 3A illustrates an exemplary two-segment turn according to someembodiments. A vehicle 390 is making the turn to transition from acurrent swath 302 to a next swath 304. The trajectory of the two-segmentturn may include a first segment 310 and a second segment 320. In thefirst segment 310, the vehicle 390 may start from a beginning position312 of the turn, move away from the next swath 304, and end at anintermediate position 314. In the second segment 320, the vehicle 390may start from the intermediate position 314, move toward the next swath304, and end at the ending position 322 of the turn.

As illustrated in FIG. 3A, the vehicle 390 may be in the forward gear(i.e., the vehicle 390 moves in the direction it is facing) during thefirst segment 310 (thus, the first segment 310 is represented by a solidline), and switch to the reverse gear (i.e., the vehicle moves in thedirection opposite to where it is facing) as it transitions to thesecond segment 320 (thus, the second segment 320 is represented by adashed line). This situation may be applicable when the vehicle 390traverses the current swath 302 in the forward gear before the turnstarted. After the turn, the vehicle 390 may traverse the next swath 304in the reverse gear.

As illustrated in FIG. 3B, if the vehicle 390 traverses the currentswath 302 in the reverse gear, the vehicle 390 may be in the reversegear during the first segment 310, and switch to the forward gear as ittransitions to the second segment 320. After the turn, the vehicle 390may traverse the next swath 304 in the forward gear. Therefore, in atwo-segment turn, the vehicle 390 may traverse the next swath 304 in agear that is opposite to that in the current swath 302 (e.g., fromforward to reverse, or from reverse to forward).

Compared to the bulb-shaped one-segment turn illustrated in FIGS. 2B and2C, the two-segment turn illustrated in FIGS. 3A and 3B may allow theentire trajectory of the turn to be confined within the headland 340even if the headland has a relatively narrow width W. Thus, crop damagemay be avoided or minimized. The two-segment turn may also allow ashorter total traveling distance during the turn as compared to abulb-shaped one-segment turn, and thus may save time and fuel cost.Therefore, the two-segment turn may be more advantageous.

FIG. 3C illustrates an exemplary two-segment turn for a compactor in aconstruction environment according to some embodiments. The short-dashedline 370 indicates a street. The dashed line 350 indicates a work area(e.g., a portion of the street 370 that needs to be compacted). Thesolid line 354 illustrates the trajectory of the compactor. Once thecompactor finishes a swath, it needs to transition to the next swath. Inthis example, the compactor makes a two-segment turn to transition froma current swath to a next swath. For example, in a first segment 362,the compactor may travel forward to an intermediate position 366, andreverse to the next swath. The compactor may progress swath by swathuntil the entire work area 350 is completed.

FIG. 4A illustrates an alternative shape of a two-segment turn accordingto some embodiments. Here, in the first segment 410 of the turn, avehicle may start from the beginning position 406 of the turn, movetoward the headland 401 and then toward the next swath 404, and end atan intermediate position 412. In the second segment 420 of the turn, thevehicle may start from the intermediate position 412 and end at theending position 408 of the turn.

FIG. 4B illustrates another alternative shape of a two-segment turnaccording to some embodiments. Here, in the first segment 430 of theturn, a vehicle may start from the beginning position 406 of the turn,move toward the headland 401 and slightly toward the next swath 404, andend at an intermediate position 432 that lies laterally about midwaybetween the current swath 402 and the next swath 404. In the secondsegment 440 of the turn, the vehicle may start from the intermediateposition 432 and end at the ending position 408 of the turn. In thiscase, in order for the entire trajectory of the two-segment turn to beconfined within the headland 401 so as to minimize crop damage, it mayrequire a wider headland as compared to the two-segment turn illustratedin FIGS. 3A-3B and 4A.

FIG. 4C illustrates a further alternative shape of a two-segment turnaccording to some embodiments. Here, in the first segment 450 of theturn, a vehicle may start from the beginning position 406 of the turn,move straight toward the headland 401, and end at an intermediateposition 452. In the second segment 460 of the turn, the vehicle maystart from the intermediate position 452, and end at the ending position408 of the turn. In this case, in order for the entire trajectory of thetwo-segment turn to be confined within the headland 401 so as tominimize crop damage, it may also require a wider headland as comparedto the two-segment turn illustrated in FIGS. 3A-3B and 4A.

FIG. 5A illustrates an exemplary three-segment turn according to someembodiments. A vehicle 590 is making the turn to transition from acurrent swath 502 to a next swath 504. The trajectory of thethree-segment turn may include a first segment 510, a second segment520, and a third segment 530. In the first segment 510, the vehicle 590may start from the beginning position 512 of the turn, move toward thenext swath 504, and ends at a first intermediate position 514. In thesecond segment 520, the vehicle 590 may start from the firstintermediate position 514, move away from the next swath 504, and endsat a second intermediate position 522. In the third segment 530, thevehicle 590 may start from the second intermediate position 522, movetoward the next swath 504, and ends at the ending position 532 of theturn.

As illustrated in FIG. 5A, the vehicle 590 may be in the forward gearduring the first segment 510, switch to the reverse gear as ittransitions to the second segment 520, and switch to the forward gearagain as it transitions to the third segment 530. This situation may beapplicable when the vehicle 590 traverses the current swath 502 in theforward gear before the turn started. After the turn, the vehicle 590may continue to traverse the next swath 504 in the forward gear.

As illustrated in FIG. 5B, if the vehicle 590 traverses the currentswath 502 in the reverse gear, the vehicle 590 may be in the reversegear during the first segment 510, switch to the forward gear as ittransitions to the second segment 520, and switch to the reverse gearagain as it transitions to the third segment 530. After the turn, thevehicle 590 may continue to traverse the next swath 504 in the reversegear. Thus, in a three-segment turn, the vehicle 590 may traverse thenext swath 504 in a gear that is the same as in the current swath 502.Therefore, if a user wishes to traverse the next swath in the same gearas in the current swath, the user may select a three-segment turn. Onthe other hand, if the user wishes to traverse the next swath in a gearthat is opposite to that in the current swath, the user may select atwo-segment turn, as discussed above with reference to FIGS. 3A and 3B.

Similar to the two-segment turn, the three-segment turn illustrated inFIGS. 5A and 5B may also allow the entire trajectory of the turn to beconfined within the headland 501 even if the headland 501 has arelatively narrow width W. Thus, crop damage may be avoided orminimized. It should be noted that multi-segment turns with more thanthree segments are also possible according to some embodiments.

Headland Following (HF) Turns

According to some embodiments, a path planner may enable a turn tofollow a headland pattern. Such a turn may be referred herein as aheadland-following (HF) turn type. In a HF turn, at least part of thetrajectory during the turn will follow a guidance line in the headland.In other words, the shape of the trajectory may adaptively changedepending on the shape of the guidance line.

FIG. 6A illustrates a one-segment HF turn according to some embodiments.The one-segment turn is for a vehicle to transition from a current swath602 to a next swath 604 (in this example, the next swath 604 is notimmediately adjacent to the current swath 602). The crop area is boundedby a guidance line 606 in the headland (i.e., a headland pattern). Inthis example, the guidance line 606 has an oval shape. In the trajectory610 of the one-segment HF turn, a vehicle may start from the beginningposition 612 of the turn, move toward the guidance line 606, then followthe guidance line 606 for some distance in the direction toward the nextswath 604, and end at the ending position 614 of the turn. Asillustrated, the trajectory 610 of the one-segment turn does not need tohave a fixed shape (e.g., a bulb-shape or a U-shape); instead, thetrajectory is adapted so that at least a portion of the trajectory 610follows the guidance line 606.

FIG. 6B illustrates another example of a one-segment HF turn accordingto some embodiments. Here, the guidance line 608 has an irregular curvedshape. In the trajectory 620 of the one-segment HF turn, a vehicle maystart from the beginning position 622 of the turn, move toward theguidance line 608, then follow the guidance line 608 for some distancetoward the next swath 604, and end at the ending position 624 of theturn. In this example, the trajectory 620 of the turn is mostly alongthe guidance line 608. Therefore, crop damage may be minimized. Incontrast, in a fixed-pattern U-shape turn, the trajectory 630 of theturn may traverse several swaths, and therefore may result in more cropdamage.

FIG. 7A illustrates a two-segment HF turn according to some embodiments.The crop area is bounded by a guidance line 706 in the headland. Thetrajectory of the two-segment turn includes a first segment 710 and asecond segment 720. In the first segment 710, a vehicle may start fromthe beginning position 712 of the turn at the current swath 702, movetoward the guidance line 706, and end at an intermediate position 714 atthe guidance line 706. In the second segment 720, the vehicle may startfrom the intermediate position 714, move along the guidance line 706 forsome distance toward the next swath 704, and end at the ending position722 of the turn. Here, again, the exact geometry of the trajectory isnot fixed; instead, it is adapted so that a portion of the trajectoryfollows the guidance line 706.

FIG. 7B illustrates another example of a two-segment HF turn accordingto some embodiments. In this example, the guidance line 780 includes asection 782 that is at an oblique angle (i.e., neither perpendicular norparallel) with respect to the direction of the swaths (e.g., the currentswath 702 and the next swath 704). In the two-segment HF-turn, a portionof the trajectory 730 follows along the guidance line 780, so that thetrajectory 730 is mostly along either a swath or the guidance line 780.Therefore, crop damage may be minimized. In contrast, in a fixed-patterntwo-segment turn, the trajectory 740 may go over the crops, andtherefore may result in more crop damage.

FIG. 8A illustrates a three-segment HF turn according to someembodiments. The crop area is bounded by a guidance line 806 in theheadland. The trajectory of the three-segment HF turn includes a firstsegment 810, a second segment 820, and a third segment 830. In the firstsegment 810, a vehicle may start from the beginning position 812 of theturn at the current swath 802, move toward the guidance line 806 in thedirection toward the next swath 804, and ends at a first intermediateposition 814 at the guidance line 806. In the second segment 820, thevehicle may start from the first intermediate position 814, move alongthe guidance line 806 for some distance in the direction away from thenext swath 804, and ends at a second intermediate position 822 at theguidance line 806. In the third segment 830, the vehicle may start fromthe second intermediate position 822, move toward the next swath 804,and ends at the ending position 832 of the turn at the next swath 804.Here, again, the exact geometry of the trajectory is not fixed; instead,it is adapted so that a portion of the trajectory (e.g., the secondsegment 820) follows the guidance line 806.

FIG. 8B illustrates another example of a three-segment HF turn accordingto some embodiments. In this example, the guidance line 880 includes asection 882 that is at an oblique angle with respect to the direction ofthe swaths (e.g., the current swath 802 and the next swath 804). In athree-segment HF turn, a portion of the trajectory 830 (e.g., the secondsegment) follows along the guidance line 880. Therefore, crop damage maybe minimized. In contrast, in a fixed-pattern three-segment turn, thetrajectory 840 may go over the crops, and therefore may result in morecrop damage.

FIG. 8C illustrates another example of a three-segment HF turn accordingto some embodiments. The trajectory of the three-segment HF turnincludes a first segment 850, a second segment 860, and a third segment870. In the first segment 850, a vehicle may start from the beginningposition 812 of the turn at the current swath 802, move toward theguidance line 806 in the direction away from the next swath 804, andends at a first intermediate position 852 at the guidance line 806. Inthe second segment 860, the vehicle may start from the firstintermediate position 852, move along the guidance line 806 for somedistance in the direction toward the next swath 804, and ends at asecond intermediate position 864 at the guidance line 806. In the thirdsegment 870, the vehicle may start from the second intermediate position864, move toward the next swath 804, and ends at the ending position 832of the turn at the next swath 804. Here, again, the exact geometry ofthe trajectory is not fixed; instead, it is adapted so that a portion ofthe trajectory (e.g., the second segment 860) follows the guidance line806.

According to some embodiments, if an HF turn is chosen, the path plannermay generate a trajectory that first takes the vehicle from its currentposition to the beginning position of the turn, then executes the turn.This feature is referred to as the move-to-start-of-turn (MST).

FIG. 9A illustrates an exemplary one-segment HF turn with the MSTfeature according to some embodiments. In this example, the vehicle 990is in the forward gear before the turn, and its current position iscloser to the guidance line 906 than the beginning position 912 of theturn. The trajectory may include a first segment 910, during which thevehicle 990 backs up (in a reverse gear) from its current position tothe beginning position 912 of the turn. During a second segment 920 ofthe trajectory, the vehicle 990 makes the turn in the forward gear fromthe beginning position 912 to the ending position 922 of the turn. Aportion of the second segment 920 follows the guidance line 906. In thisexample, although it is a one-segment turn type, the trajectory of thevehicle 990 includes two segments due to the MST feature.

FIG. 9B illustrates an exemplary two-segment HF turn with the MSTfeature according to some embodiments. In this example, the vehicle 990is in the forward gear before the turn, and its current position isfarther away from the guidance line 906 than the beginning position 912of the turn. The trajectory may first take the vehicle 990 from itscurrent position to the beginning position 922 of the turn in theforward gear, then executes a first segment 930 of turn in the forwardgear, followed by a second segment 940 of the turn in the reverse gear.In this example, the trajectory includes only two segments; that is, thetrajectory from its current position to the beginning position 922 ofthe turn and the first segment 930 of the turn are considered as onesegment, since the vehicle 990 is in the same gear therethrough. On theother hand, if the vehicle's current position is closer to the guidanceline 906 than the beginning position 922 of the turn, the trajectory mayinclude three segments.

The MST feature may also be applied to three-segment turns in a similarfashion.

According to some embodiments, a user may select amove-to-end-of-swath-before-turn (MESBT) option. If the MESBT option isturned on, a path planner may produce a trajectory in which the vehiclefirst moves from its current position to an end position of the currentswath, then moves from the end position of the current swath to thebeginning position of the turn, then executes the turn. The MESBTfeature may be applied to one-segment turns, as well as to multi-segmentturns with two or more segments.

FIG. 10 illustrates an exemplary two-segment turn that follows aheadland pattern with the MESBT feature according to some embodiments.In this example, the vehicle 1090 is in the forward gear facing the endof the swath 1022. The trajectory generated by a path planner may firsttake the vehicle 1090 from its current position to the end of the swath1022 in the forward gear, then back to the beginning position 1012 ofthe turn in the reverse gear, then executes the first segment 1030 ofthe turn in the forward gear, followed by the second segment 1040 of theturn in the reverse gear. Thus, in this example of a two-segment turn,the trajectory effectively includes four segments. The segment 1010 thattakes the vehicle 1090 from its current position to the end of the swath1022, and the segment 1020 (almost overlaying the segment 1010) thattakes the vehicle 1090 from the end of the swath 1022 to the beginningposition 1012 of the turn may be referred to as initial segments.

According to some embodiments, a user may select amove-to-beginning-of-next-swath-after-turn (MBSAT) option. If the MBSAToption is turned on, a path planner may produce a trajectory in which,after the turn has been completed, the vehicle moves from the endingposition of the turn to the beginning of the next swath. The MBSATfeature may be applied to one-segment turns, as well as multi-segmentturns with two or more segments. The MBSAT option may be appliedindependently, or in combination with the MESBT option.

FIG. 11 illustrates an exemplary three-segment HF turn with both theMESBT feature and the MBSAT feature according to some embodiments. Thetrajectory may first take the vehicle 1190 from its current position tothe end of the swath 1114, then back to the beginning position 1112 ofthe turn, then executes the three-segment turn 1130 ending at the endingposition 1142 of the turn, then to the beginning 1144 of the next swath.The segment 1110 that takes the vehicle 1190 from its current positionto the end of the swath 1114, and the segment 1120 (almost overlayingthe segment 1110) that takes the vehicle 1190 from the end of the swath1114 to the beginning position 1112 of the turn may be referred to asinitial segments. The segment 1140 that takes the vehicle 1190 from theending position 1142 of the turn to the beginning of the next swath 1144may be referred to as the final segment. Thus, in this example, theentire trajectory of the three-segment turn effectively includes sixsegments: two initial segments, one final segment, plus three segmentsin the turn.

According to some embodiments, a user may select a turn-within-boundary(TWB) option for one-segment turns, as well as for multi-segment turns.The TWB option may be available when the headland-following (HF) optionis turned off (if the HF option is turned on, the TWB may beautomatically on).

FIG. 12 illustrates exemplary two-segment turns with the TWB optionturned on and off, respectively. The work area is bounded by a boundary1208, which may be a geofence. A guidance line 1206 may be inwardlyoffset from the boundary 1208. When the TWB option is turned off, atrajectory 1210 of a two-segment turn may go beyond the boundary 1208.When the TWB option is turn on, a trajectory 1220 of a two-segment turnmay be confined within the boundary 1208. (Note that, if the HF optionis turned on, a trajectory of a two-segment turn may partially followthe guidance line 1206, e.g., as illustrated in FIG. 7A, whicheffectively confines the trajectory within the boundary 1208.) In someembodiments, a path-planning algorithm may treat the boundary 1208 as anobstacle and perform trajectory optimization with obstacle avoidance, inwhich the shape of the turn may be changed so as to avoid the obstacles.

Although the examples illustrated above show straight swaths, thevarious embodiments discussed above can be applied to curved swaths aswell. FIG. 13A illustrates an example of a one-segment turn 1310 from acurrent swath 1312 to a next swath 1314, both of which are curved.

According to various embodiments, the turns (including one-segment turnsand multi-segment turns) can have arbitrary shapes. FIG. 13B illustratesan example of a one-segment turn 1320 from a current swath 1322 to anext swath 1324. In this example, both the current swath 1322 and thenext swath 1324 are curved. As illustrated, the one-segment turn 1320 inthis example does not have a fixed bulb shape.

The various embodiments discussed above can also be applied to swathsthat are not parallel to each other. FIG. 13C illustrates an example ofa one-segment turn 1330 from a current swath 1332 to a next swath 1334,wherein the current swath 1332 and the next swath 1334 are not parallelto each other. FIG. 13D illustrates another example of a one-segmentturn 1340 from a current swath 1342 to a next swath 1344, wherein thecurrent swath 1342 and the next swath 1344 are not parallel to eachother. The trajectory of the turn can be an arbitrary shape. Forexample, it can be a bulb-like shape as illustrated in FIG. 13D, or aU-like shape as illustrated in FIG. 13C, or it can be any other shape.The path-planning algorithms may determine an optimal trajectory thatmeets certain optimization criteria regardless of the shape of thetrajectory.

FIG. 14 shows an exemplary user interface (UI) for a user to select adesired type of turn according to some embodiments. The user interfacemay be implemented as selectable options on a display, or as hardwarebuttons.

The user may select one of the options “1-seg,” “2-seg,” or “3-seg” toselect a one-segment turn, a two-segment turn, or a three-segment turn.Only one of the options can be selected. If no option is selected, thedefault may be a one-segment turn.

The “HF” (headland-following) option is a toggle button that can beturned on or off.

The “TWB” (turn-within-boundary) option is a toggle button that can beturned on or off if the “HF” option is turned off. If the “HF” option isturned on, “TWB” is automatically turned on.

The “MESBT” (move-to-end-of-swath-before-turn) option is a toggle buttonthat can be turned on or off if “HF” is on. According to someembodiments, if “HF” is turned off, the MESBT option will not beavailable (i.e., it cannot be turn on).

The “MBSAT” (move-to-beginning-of-next-swath-after-turn) option is atoggle button that can be turned on or off if “HF” is on. According tosome embodiments, if “HF” is turned off, the MBSAT option will not beavailable (i.e., it cannot be turn on).

When the “Request Turn” button is pressed, a command will be sent to thepath planner for generating a trajectory for the requested type of turn.According to some embodiments, the generated trajectory may be displayedon a display screen.

In a path planning algorithm for an autonomous vehicle, the inputs mayinclude a start position, a desired goal position, and mechanicalconstraints of the vehicle. Given these inputs, the algorithm may seekto find an optimal path from the start position to the goal positionunder certain optimization criteria. Exemplary optimization criteria mayinclude traveling distance, coverage area, fuel efficiency, and thelike.

FIGS. 15A and 15B illustrate schematically a vehicle model. The vehicleincludes front wheels 1510 and 1520, and rear wheels 1530 and 1540. Therear wheels 1530 and 1540 are separated from each other by a width w.The front wheels and the rear wheels are separated by a distance l. Inan active front steering integrated chassis control system, theeffective steering angle ϕ may be between the steering angles of theleft and right front wheels ϕ_(o) and ϕ_(i). Vehicle mechanicalconstraints may include the velocity of the vehicle, the slew rate ofthe vehicle (i.e., the rate of change of steering angle), maximumsteering angle, the length of the vehicle, and the like, as well as thefootprint and the mechanical constraints of an attached implement. Thedynamic motion of the vehicle may be expressed as,s _(t+1) =F(s _(t) ,u _(t)),where s_(t) is the current pose at time t, which may include the (x, y,yaw, curvature, and the like) coordinates; s_(t+1) is the future pose att+1; and u_(t) is the action, which may include speed, steering, and thelike. Curvature of a vehicle is a path planning entity that relates tothe steering angle and wheelbase of the vehicle. For example, if thesteering angle is high, then curvature is high, and if the steeringangle is low then the curvature is low. In some embodiments, thecurvature may be defined as the tangent of the steering angle divided bythe wheelbase.

According to some embodiments, search-based methods may be used for pathplanning. Search techniques may include blind search techniques (e.g.,depth first search (DFS), breadth first search (BFS), and the like), andheuristic search techniques (e.g., hill climbing search, best-firstsearch, greedy search, A* search, and the like).

Path planning for turns from one swath to a next swath may optimizedistance from a start pose of the vehicle (or its implement) to adesired goal pose of the vehicle. Such path planning may involve fourtypes of trajectory optimization: point-to-point, point-to-linestring,linestring-to-point, and linestring-to-linestring, as illustrated inFIGS. 16A-16D. A point may comprise a pose. A linestring may comprise asequence of points. For example, point-to-point trajectory optimizationmight be used for a turn in which the aim is to find the shortestfeasible single segment from one point on start swath to another pointon the goal swath (for example an adjacent point on the next swath).Linestring-to-linestring trajectory optimization might be used for anend of-row-turn in which the aim is to find the shortest feasible singlesegment turn that is within the boundary and can go as close as possibleto the end of current swath and as close as possible to the beginning ofnext swath. As another example, point-to-linestring or alinestring-to-point trajectory optimization may be used in a two-segmentturn. There, the aim may be to go from the vehicle's current position(which is a point) to the portion of the headland in front of thevehicle (which is a linestring); then the vehicle reverses from itscurrent position on the headland (which is a point) to the next swath(which is a linestring).

FIG. 17 shows a simplified diagram of a system 1700 for an autonomousvehicle according to some embodiments. The system 1700 may include apath planning module 1780, and a user interface 1750. The user interface1750 may allow a user to request and accept a turn, and to specify atype of turn, as discussed above. In some embodiments, the userinterface 1750 may also include a display.

The path planning module 1780 may include one or more computerprocessors configured to determine a trajectory for the requested turnaccording to the various embodiments as discussed above. In someembodiments, the trajectory may be displayed in a display (e.g., thedisplay in the user interface 1750). The path planning module 1780 mayalso be configured to perform other navigation planning and/or coverageplanning (e.g., planning the trajectories of the swaths) for theautonomous vehicle.

The system 1700 may include a memory 1790. The memory 1790 may storeinformation needed for the path planning module 1780, as well as otherinformation. For example, the memory 1790 may store information about awork area, such as a boundary (e.g., a geofence) and headland patterns(i.e., guidance lines). The memory 1790 may also store information ofthe swaths (which may be predetermined or generated by the path planningmodule 1780). The memory 1790 may also store computer-executableinstructions to be executed by the computer processors of the pathplanning module 1780. The memory 1790 may comprise a volatile memoryrandom access memory (RAM), or non-volatile data storage device such asa hard disk drive, flash memory or other optical or magnetic storagedevice. In some embodiments, the path planning module 1780 may includeits own memory.

The system 1700 may include a global navigation satellite systems (GNSS)antenna 1720 attached to the autonomous vehicle, and a GNSS receiver1710 coupled to the GNSS antenna 1720. The GNSS receiver 1710 may beconfigured to determine a current position of the vehicle based on thesatellite signals received from GNSS satellites. In some embodiments,the system 1700 may also include an optional position correction system1730. The position correction system 1730 may include an antenna 1732and a receiver 1734 for receiving correction data from a referencestation or a network of reference stations. For example, the positioncorrection system 1730 may include a differential global positioningsystem (DGPS). The correction data may be used by the GNSS receiver 1710to determine a more precise position of the vehicle (e.g., to millimeteror sub-millimeter accuracies). In some embodiments, the GNSS receiver1710 may be an independent unit separate from the system 1700.

The system 1700 may include other sensors 1740. For example, the othersensors 1740 may include LiDAR sensors for obstacle detection, inertialmeasurement units or IMUS (e.g., accelerometers and gyroscopes), wheelangle sensors, and the like.

The system 1760 may include a vehicle controller 1760. The vehiclecontroller 1760 may be configured to operate the vehicle based on thesensor data (e.g., including GNSS data and other sensor data) and thetrajectories determined by the path planning module 1780. For example,the path planning module 1780 may output a trajectory for a turn, alongwith a speed profile and optionally an implement profile for thetrajectory, to the vehicle controller 1760, so that the vehiclecontroller 1760 may execute the turn according to the trajectory. Thespeed profile includes a respective speed for each respective point ofthe plurality of points.

In some embodiments, the various components of the system 1700 may beinterconnected with each other via a bus 1702. In some otherembodiments, the various components may be connected with each other inother ways.

FIG. 18 is a simplified flowchart illustrating a method 1800 of pathplanning for an autonomous vehicle to make a turn according to someembodiments.

The method 1800 includes, at 1802, receiving a request for a two-segmentturn of a vehicle from a current swath to a next swath in a work area,and at 1804, in response to receiving the request, receiving informationof the current swath and information of the next swath.

The method 1800 further includes, at 1806, determining a trajectory ofthe turn based on the information of the current swath and theinformation of the next swath. The trajectory includes a first segmentand a second segment. The first segment starts from a beginning positionof the turn at the current swath and ends at an intermediate position;and the second segment starts from the intermediate position and ends atan ending position of the turn at the next swath. The vehicle changesfrom a forward gear to a reverse gear, or vice versa, as the vehicletransitions from the first segment to the second segment.

The method 1800 further includes outputting the trajectory to a controlsystem of the vehicle for executing the turn by following the firstsegment and the second segment of the trajectory successively.

It should be appreciated that the specific steps illustrated in FIG. 18provide a particular method of path planning for an autonomous vehicleto make a turn according to some embodiments. Other sequences of stepsmay also be performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 18 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 19 is a simplified flowchart illustrating a method 1900 of pathplanning for an autonomous vehicle to make a turn according to someembodiments.

The method 1900 includes, at 1902, receiving a request for athree-segment turn of a vehicle from a current swath to a next swath ina work area. The request specifies that the turn is to follow a guidanceline in a headland at a periphery of the work area. The method 1900further includes, at 1904, in response to receiving the request,receiving information of the current swath, information of the nextswath, and information of the guidance line.

The method 1900 further includes, at 1906, determining a trajectory ofthe turn based on the information of the current swath, the informationof the next swath, and the information of the guidance line. Thetrajectory includes a first segment, a second segment, and a thirdsegment. The first segment starts from a beginning position of the turnat the current swath and ends at a first intermediate position on theguidance line. The second segment starts from the first intermediateposition, moving along the guidance line, and ends at a secondintermediate position on the guidance line. The vehicle changes from aforward gear to a reverse gear, or vice versa, as the vehicletransitions from the first segment to the second segment. The thirdsegment starts from the second intermediate position and ends at anending position of the turn at the next swath. The vehicle changes fromthe reverse gear to the forward gear, or vice versa, as the vehicletransitions from the second segment to the third segment.

The method 1900 further includes, at 1908, outputting the trajectory toa control system of the vehicle for executing the turn by following thefirst segment, the second segment, and the third segment of thetrajectory successively.

It should be appreciated that the specific steps illustrated in FIG. 19provide a particular method of path planning for an autonomous vehicleto make a turn according to some embodiments. Other sequences of stepsmay also be performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 19 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 20 is a simplified flowchart illustrating a method 2000 of pathplanning for an autonomous vehicle to make a turn according to someembodiments.

The method 2000 includes, at 2002, receiving a request for a turn of avehicle from a current swath to a next swath in a work area. The workarea has a headland at a periphery thereof. The headland characterizedby a guidance line therethrough. The method 2000 further includes, at2004, in response to receiving the request, receiving information of thecurrent swath, information of the next swath, and information of theguidance line.

The method 2000 further includes, at 2006, determining a trajectory ofthe turn based on the information of the current swath, the informationof the next swath, and the information of the guidance line. Thetrajectory includes one or more segments. At least a portion of a firstsegment of the one or more segments follows the guidance line in theheadland. The method 2000 further includes, at 2008, outputting thetrajectory to a control system of the vehicle for executing the turn.

It should be appreciated that the specific steps illustrated in FIG. 20provide a particular method of path planning for an autonomous vehicleto make a turn according to some embodiments. Other sequences of stepsmay also be performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 20 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A method of path planning for an autonomousvehicle, the method comprising: receiving a request for a two-segmentturn of a vehicle from a current swath to a next swath in a work areadefined by a geofence, the request specifying the two-segment turn atleast partially follows a guidance line in a headland at a periphery ofthe work area, wherein: the vehicle has an implement attached thereto;the headland has a width extending between the geofence and an innerboundary of the headland; and the guidance line is offset from the innerboundary of the headland by approximately one half the width of theimplement; in response to receiving the request, receiving informationof the current swath and information of the next swath; determining atrajectory of the two-segment turn based on the information of thecurrent swath and the information of the next swath, the trajectoryincluding a first segment and a second segment, wherein: the firstsegment starts from a beginning position of the two-segment turn at thecurrent swath and ends at an intermediate position; and the secondsegment starts from the intermediate position and ends at an endingposition of the two-segment turn at the next swath, wherein the vehiclechanges from a forward gear to a reverse gear, or vice versa, as thevehicle transitions from the first segment to the second segment; andoutputting the trajectory to a control system of the vehicle forexecuting the two-segment turn by following the first segment and thesecond segment of the trajectory successively.
 2. The method of claim 1,wherein the request specifies the two-segment turn to be within theheadland, the method further comprising: receiving information of theheadland; wherein determining the trajectory of the two-segment turn isperformed further based on the information of the headland, and whereinthe trajectory of the two-segment turn is confined within the headland.3. The method of claim 1, further comprising: receiving information ofthe guidance line; wherein determining the trajectory of the two-segmentturn is performed further based on the information of the guidance line,and wherein at least a portion of the second segment of the trajectoryfollows the guidance line.
 4. The method of claim 3, further comprising:receiving a current position of the vehicle; wherein determining thetrajectory of the two-segment turn is performed further based on thecurrent position of the vehicle, and wherein the trajectory furtherincludes a third segment that starts from the current position of thevehicle and ends at the beginning position of the two-segment turn, andthe third segment is to be executed before the first segment and thesecond segment are executed.
 5. The method of claim 3, wherein therequest specifies moving to an end position of the current swath beforethe two-segment turn, and wherein determining the trajectory of thetwo-segment turn is performed further based on the end position of thecurrent swath, and the trajectory further includes: a third segment thatstarts from a current position of the vehicle and ends at the endposition of the current swath; and a fourth segment that starts from theend position of the current swath and ends at the beginning position ofthe two-segment turn; wherein the third segment and the fourth segmentare to be executed successively before the first segment and the secondsegment are executed.
 6. The method of claim 3, wherein the requestspecifies moving to a beginning position of the next swath after thetwo-segment turn, and wherein determining the trajectory of thetwo-segment turn is performed further based on the beginning position ofthe next swath, and the trajectory further includes: a third segmentthat starts from the ending position of the two-segment turn and ends atthe beginning position of the next swath, wherein the third segment isto be executed after the first segment and the second segment areexecuted.
 7. The method of claim 3, wherein the guidance line is curved.8. The method of claim 1, wherein determining the trajectory of thetwo-segment turn is performed such that a total distance traversed bythe vehicle along the first segment and the second segment is minimized.9. The method of claim 1, wherein at least one of the current swath andthe next swath is curved.
 10. The method of claim 1, wherein the currentswath and the next swath are parallel to each other, or not parallel toeach other.
 11. The method of claim 1, wherein: in response todetermining that the vehicle is traversing the current swath in theforward gear before the two-segment turn, determining gear settings ofthe vehicle during the two-segment turn such that the vehicle traversesthe first segment in the forward gear, and traverses the second segmentin the reverse gear; and in response to determining that the vehicle istraversing the current swath in the reverse gear before the two-segmentturn, determining the gear settings of the vehicle during thetwo-segment turn such that the vehicle traverses the first segment inthe reverse gear, and traverses the second segment in the forward gear.12. The method of claim 1, wherein the trajectory includes a pluralityof points, each respective point of the plurality of pointscharacterized by a respective two-dimensional spatial coordinate, arespective yaw angle, and a respective curvature of the vehicle, and themethod further comprising: determining a speed profile along thetrajectory, the speed profile including a respective speed for eachrespective point of the plurality of points; and outputting the speedprofile to the control system of the vehicle.
 13. The method of claim 1,further comprising: determining an implement profile along thetrajectory; and outputting the implement profile to the control systemof the vehicle.
 14. The method of claim 1, further comprising:displaying the trajectory on a user display.
 15. A method of pathplanning for an autonomous vehicle, the method comprising: receiving arequest for a three-segment turn of a vehicle from a current swath to anext swath in a work area defined by a geofence, the request specifyingthe three-segment turn to follow a guidance line in a headland at aperiphery of the work area, wherein: the vehicle has an implementattached thereto; the headland has a width extending between thegeofence and an inner boundary of the headland; and the guidance line isoffset from the inner boundary of the headland by approximately one halfthe width of the implement; in response to receiving the request,receiving information of the current swath, information of the nextswath, and information of the guidance line; determining a trajectory ofthe three-segment turn based on the information of the current swath,the information of the next swath, and the information of the guidanceline, the trajectory including a first segment, a second segment, and athird segment, wherein: the first segment starts from a beginningposition of the three-segment turn at the current swath and ends at afirst intermediate position on the guidance line; the second segmentstarts from the first intermediate position, moving along the guidanceline, and ends at a second intermediate position on the guidance line,wherein the vehicle changes from a forward gear to a reverse gear, orvice versa, as the vehicle transitions from the first segment to thesecond segment; and the third segment starts from the secondintermediate position and ends at an ending position of thethree-segment turn at the next swath, wherein the vehicle changes fromthe reverse gear to the forward gear, or vice versa, as the vehicletransitions from the second segment to the third segment; and outputtingthe trajectory to a control system of the vehicle for executing thethree-segment turn by following the first segment, the second segment,and the third segment of the trajectory successively.
 16. The method ofclaim 15, wherein the guidance line is curved.
 17. The method of claim15, wherein at least one of the current swath and the next swath iscurved.
 18. The method of claim 15, wherein the current swath and thenext swath are parallel to each other, or not parallel to each other.19. The method of claim 15, further comprising: receiving a currentposition of the vehicle; wherein determining the trajectory of thethree-segment turn is performed further based on the current position ofthe vehicle, and wherein the trajectory further includes a fourthsegment that starts from the current position of the vehicle and ends atthe beginning position of the three-segment turn, and the fourth segmentis to be executed before the first segment, the second segment, and thethird segment are executed.
 20. The method of claim 15, wherein therequest specifies moving to an end position of the current swath beforethe three-segment turn, and wherein determining the trajectory of thethree-segment turn is performed further based on the end position of thecurrent swath, and the trajectory further includes: a fourth segmentthat starts from a current position of the vehicle and ends at the endof the current swath; and a fifth segment that starts from the end ofthe current swath and ends at the beginning position of thethree-segment turn; and wherein the fourth segment and the fifth segmentare to be executed successively before the first segment, the secondsegment, and the third segment are executed.
 21. The method of claim 19,wherein the request specifies moving to a beginning position of the nextswath after the three-segment turn, and wherein determining thetrajectory of the three-segment turn is performed further based on thebeginning position of the next swath, and the trajectory furtherincludes: a fifth segment that starts from the ending position of thethree-segment turn and ends at the beginning position of the next swath,wherein the fifth segment is to be executed after the first segment, thesecond segment, the third segment and the fourth segment are executed.22. The method of claim 15, wherein: in the first segment of thetrajectory, the vehicle moves from the beginning position of thethree-segment turn toward the guidance line and in a direction towardthe next swath; in the second segment of the trajectory, the vehiclemoves from the first intermediate position along the guidance line in adirection toward the current swath to the second intermediate position;and in the third segment of the trajectory, the vehicle moves from thesecond intermediate position toward the next swath.
 23. The method ofclaim 15, wherein: in the first segment of the trajectory, the vehiclemoves from the beginning position of the three-segment turn toward theguidance line and in a direction away from the next swath; in the secondsegment of the trajectory, the vehicle moves from the first intermediateposition along the guidance line toward the next swath to the secondintermediate position; and in the third segment of the trajectory, thevehicle moves from the second intermediate position toward the nextswath.
 24. The method of claim 15, wherein determining the trajectory ofthe three-segment turn is performed such that a total distance traversedby the vehicle along the first segment, the second segment, and thethird segment is minimized.